Chapter 2 Communicating Over the Network Modified by Profs. Chen and Cappellino.

Chapter 2Communicating Over the Network

Modified by Profs. Chen and Cappellino

Objectives

This chapter prepares you to: Describe the structure of a network, including the

devices and media that are necessary for successful communications.

Explain the function of protocols in network communications.

Explain the advantages of using a layered model to describe network functionality.

Describe the role of each layer in two recognized network models: The TCP/IP model and the OSI model.

Describe the importance of addressing and naming schemes in network communications.

The three Elements of Communication

The first - message ___________, or sender.

The second -________________, or receiver receives the message and interprets it.

A third - a __________________the media that provides the pathway over which the message can travel from source to destination.

Communicating the Messages In theory, a single communication, such as a an

e-mail message, could be sent across a network from a source to a destination as one massive continuous stream of bits.

Why is this not a good idea? The solution: divide data into

_____________, more manageable pieces to send over the network.

This division of the data stream into smaller pieces is called ___________________.

Communicating the Messages Segmenting messages has two primary

benefits.First, many ___________________________ _________ or mixed together on the network.

The process used to mix together the pieces of separate and distinct conversations on the network is called ______________.

Second, segmentation can _______________ ______________ of network communications.

Separate pieces need __________________________ across the network from source to destination.

If part of the message fails to make it to the destination, _______ __________________________________________________

Communicating the Messages Disadvantage of segmentation and

multiplexing ______________________________________

Each packet must be individually addressed and numbered

Then reassembled into the content of the original message.

Devices throughout the network and protocols ensure that the pieces of the message arrive reliably at their destination.

Components of the Network _____________________ are the physical elements

or _____________________ of the network. Can you list some examples of devices? Can you list some examples of media?

_______________________________________ that run on the networked devices.

Services include ______________________________ we use. What are some examples?

____________________________________ that directs and moves the messages through the network

The set of rules which help determine what goes where ______________________ consist of ___________

or _________________________ (more to come…)

End Devices and their Role on the Network

Example of end devices:____________________________ (work stations, laptops, file servers, web servers)

Network ___________________________________________________Security cameras__________________________________ (such as wireless barcode scanners, PDAs)

End devices are referred to as ______________. A host can act as a client, a server, or both.

______ have software installed that enables them to provide information and services, like e-mail or web pages, to other hosts on the network.

Network computer that responds to client requests for network resources _____________________________________ obtained from the server.

Intermediary Devices and their Role on the Network

Networks rely on ___________________________ _______________________ and ensure that data flows to destination

work behind the scenes Examples of intermediary network devices are:

_________________________ Devices (____________ __________________, and wireless access points)

_______________________________ (____________)Communication Servers and Modems_______________________ (_________________)

In managing data, _________________ devices use the ___________________________, in conjunction with information about the network interconnections, in path determination

Processes possibly running on some or all the intermediary network devices are:

_____________________________________________________________ about what _________________________________

_____________________ other devices ____________ and communication failures

Direct data along __________________________ when there is a link failure

Classify and direct messages according to QoS priorities

__________________________________, based on security settings – ACL’s

Intermediary Devices and their Role on the Network

Network Media Communication across a

network- from source to destination is carried on a _____________________.

These media are: ____________ within cables

Data sent via ___________ pulses ___________________ (fiber optic cable)

Data sent via ________________ ______________ transmission

Data sent via electromagnetic _________________

Network Media Different types of network media have different

features and benefits. The ___________________ the media can

successfully carry a signal _____________ can carry a signal the farthest

The __________ in which the media is to be installed ___________ best in “noisy” environments

The ________________________ at which it must be transmitted.

Cat 5 can go fairly high and is often very sufficient but fiber is best

The ________________ of the media and installation ________________ is most costly!

Network Infrastructures Vary greatly in terms of:

The size of the area coveredThe number of users connectedThe number and types of services available

Different types include:___________ (Local Area Networks)___________ (Wide Area Networks)___________ (Storage Area Networks)ETC

Local Area Networks An individual ______________

network __________________________

_____________________providing services to people within a __________________________,

single business, campus or region. Administered by a ___________

______________________The administrative control that governs the security and access control policies are enforced on the _______________________

Ie. – under control of that business itself

Wide Area Networks __________________________

________________________ Typically _________________

capacityslower than LAN’s

_____________ (businesses) that are at distant locations

businesses generally use a _________________________ ___________ (TSP) to interconnect the LANs at the different locations.

WANs use specifically designed network devices to make the interconnections between LANs.

The Internet – A Network of Networks Enables user to communicate with a resource on

another network, outside of our local organization. Internetwork (aka Network)

The most well-known and publicly-accessible internetwork is the Internet.

Internet Service Provider (ISP) networks _____________ _________________ to help form the Internet

Use generally accepted standards and protocols

Intranet Refers to ____________________________________ ___________________________________________ _______________________, or others with authorization.

Accessed internally or remotely

Network Representations

Recall “Elements of a Network” from Chapter 1

We will be using visual representations often so please commit them to memory

Additional important terms:______________________ - A NIC, or LAN

adapter, provides the ________________ __________________ or other host device.

The media connection plugs directly into the NIC.

Physical Port - A _________ or outlet on a networking device ___________________ ___________________

Interface - Specialized ports on an internetworking device ________________ _________________________________

the ports on a router are referred to _____________________

Rules that Govern Communications For successful communication,

_____________________________ must be followed by both parties

These protocols are ________________ ______________________ that is loaded on each host and network device.

Easy way to think of protocols interacting with each other to help move data along, is to think of a stack or layered hierarchy.

Each __________________________ depends on the functionality defined by the ____________________________

Higher level protocols focus on message being sent and user interface

The ____________________ of the stack are concerned with __________________ __________________________

Network Protocol Suite: ____________________________________

______________________________ used in a computer network

Example: ________________protocol suite Must describe precise requirements and

interactions such as:The ______________ or structure of the messageThe ____________ by which networking devices share information about pathways with other networks

How and when __________ and system messages are ______________________________

The ___________________ of data transfer sessions

Proprietary Network Protocols

Individual protocols in a protocol suite _____ _________________________________

_______________ or vendor ___________ the definition of the protocol and how it functions.

Not so with the TCP/IP protocol suite ________________________________

Industry Standards- A process or protocol that ______________

_________________________ and ratified by a ________________________

Ex: the Institute of Electrical and Electronics Engineers (IEEE) or the Internet Engineering Task Force (IETF).

Use of standards ensures that products _____ ____________________________________ for efficient communications.

Can anyone think of an example of a product/process or protocol that is considered standard?

Example: interaction of protocols between

a web server and a web browser. ___________________________:

Hypertext Transfer Protocol (HTTP) is a protocol that governs the way that a web server and a web client interact.

HTTP defines first- the content and formatting of the requests and second- the responses exchanged between client and server.

How are the messages transported?... ___________________________:

______________________________ ________________________________ ________________ - in this example- between web servers and web clients

TCP divides the HTTP messages into __________ _________________________, to be sent to the destination client.

TCP also controls the rate at which messages are exchanged.

Example: interaction of protocols CONT…

____________________________: Internet Protocol (IP) is responsible for taking the

segments (from upper transport layer), ___________________________, _______ ___________________________________

Then selecting the ________________________ to the destination host.

________________________________: Network access protocols describe two primary

functions, _____________________ and the ______________________ of data on the media.

Data-link management protocols take the packets from IP (the above layer) and format them to be transmitted over the media. The standards and protocols for the physical media govern ______________________________________________ and how they are interpreted by the receiving clients.

Transceivers on the network interface cards (NICs) implement the appropriate standards for the media that is being used.

Technology Independent Protocols Networking protocols describe the _______

__________ during network communications. Protocols generally __________________

________________ a particular function. This is why many protocols are said to be

___________________________This means that a computer - and other devices – can, for example, access a web page stored on any type of web server (IIS, Apache, etc) that uses any form of operating system (Windows, MAC, Linux) from anywhere on the Internet.

The Benefits of Using Layered Model ________________________

protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below.

_________________ because products from different vendors can work together.

_____________ technology or capability _______________________________ _______________ above and below.

________________ to describe networking functions and capabilities.

Helps us visualize and __________ about networking and protocol interaction

Protocol and Reference Models

There are two basic types of networking models: protocol models and reference models.

A _______________ model: provides a model that ________ ________________________________________________.

The hierarchical set of related protocols in a suite typically represents all the functionality required to interface the human network with the data network.

The ____________________ (seen in previous example) is a protocol model because it describes the functions (and protocols) that occur at each layer of the TCP/IP suite. ________ Model

Protocol and Reference Models A _______________ model:

helps provide ____________ _______________________ involved in all types of network protocols and services. Not intended to provide a sufficient

level of detail to define precisely the services of the network architecture.

The _________________________ ___________ is the most widely known internetwork reference model.

Used in ___________, operation specifications, and troubleshooting.

________ Model

The TCP/IP Model It defines ________ categories

of functions (in layers) that must occur for communications to be successful.

An _____________________ ________________________

________________________ over definitions and standards of the model

Definitions and standards (including use of the protocols) defined in a publicly-available set of documents

_____________________________

Please memorize the functions

represented at leach layer

Communication Process (through the TCP/IP model)

A complete communication process includes these steps:1. _____________ at the application layer of the __________

device2. __________________________________ of data as it passes

down the protocol stack in the source end device 3. Generation of the data _______________________ at the

network access layer of the stack4. _____________________________________________, which

consists of media and any intermediary devices5. _________________ of the data at the network access layer of

the _____________________ device 6. _____________________ of the data as it passes up the stack in

the destination device 7. Passing this data to the destination application at the Application

layer of the destination device

Protocol Data Units and Encapsulation ______________________

__________________________ _______________________

The encapsulation process: As application data is passed down the protocol stack various ________________________ to it _______________________.

The form that a piece of data takes at any layer is called a _______________________

During encapsulation, each succeeding layer encapsulates the PDU that it _____________ __________________ in accordance with the protocol being used.

Protocol Data Units and Encapsulation At each stage of the process, a

PDU has a different name to reflect its new appearance. ______ - The general term for the

PDU used at the _____________ ________ - _____________ PDU _________ - _______________

Layer PDU ____________ - _____________

___________ PDU ______________ - A PDU used

when __________________ data over the medium

The Sending and Receiving process (from Web Server to client)

In the web server example from earlier: The Application layer: HTTP begins the process by delivering the

HTML web page data to the Transport layer. The Transport layer: The application data is broken into TCP

segments. Each TCP segment is given a label, _____________, containing information

about which process running on the destination computer should receive the message.

The Transport layer: encapsulates the web page HTML data within the segment and sends it to the Internet layer,

The Internet layer: Here the entire TCP segment is encapsulated within an IP packet, which adds another label, called the IP header.

The IP header contains source and destination IP addresses. The Network Access layer: Using the Ethernet protocol, the

packet is encapsulated within a frame header and trailer. Frame header contains source and destination physical address. The trailer contains error checking information. Finally the bits are encoded onto the Ethernet media by the server NIC.

This process is reversed at the receiving host.Data travels up the layers of the model

The OSI Model Designed by the ______________

________________________________________ (ISO)

Provides an extensive list of functions and services that can occur at each layer.

It also describes the ____________ _________________________________________________________

NOTE: Although the content of this course

will be structured around the OSI Model

the focus of discussion will be the protocols identified in the TCP/IP protocol stack.

Supplementary OSI layer slides

AALL LL PPEOPLE EOPLE S SEEM EEM TTOO NNEED EED DDATA ATA PPROCESSINGROCESSING

7. The Application Layer _______________________________

________________________ provides general network access

Directly supports user applications The OSI layer ____________________ Applications it supports are outside the

OSI layer modelExample of applications:

________________________________

6. The Presentation Layer

Ensures that data sent by the application layer of one system is readable by the application layer of another system

________ the way data is _____________ __________________________

5. The Session Layer

____________________________ _____________________ between applications on different computers

4. The Transport Layer

Segments data from the sending host & reassembles data on the receiving host

____________________________________________________________________________________________.Error detection-and-recovery Information flow control Involved in Quality Of Service, Reliability

3. The Network Layer _________________________________

______________ between two end systemsbased on network conditions, priority of

service etc __________________ occurs at this layer __________________ occurs at this layer

2. The Data Link Layer Provides reliable __________________

______________________ (media) ______________ (vs. logical)addressing Cyclical redundancy check (_______)

allows for __________________________

1. The Physical Layer Defines the _______________________

__________________________ specifications for the ______________Wires, connectors, voltages, data rates

Transmits ______________________ over the physical medium

Comparing the OSI and TCP/IP Model The key parallels between the two models occur at

the OSI model _______________________ L3 of OSI deals with addressing and routing of

messages The ___________________ is the TCP/IP suite protocol

that includes the functionality described at ___________ Functions at L4 of OSI include acknowledgement,

error recovery, and sequencing. ______________________________ includes the

functionality described at ________________ Application layer and the Network Access layer of the

TCP/IP model are further detailed in the OSI model At the TCP/IP Network Access Layer,

the TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium; it only describes the handoff from the Internet Layer to the physical network protocols.

The TCP/IP Application layer OSI model Layers 5, 6 and 7 are used as references for application software developers and vendors to produce products that need to access networks for communications.

Addressing in the Network The OSI model describes the processes of

encoding, formatting, segmenting, and encapsulating data for transmission over the network.

Using the OSI model as a guide, we can see the different addresses and identifiers that are necessary at each layer.

Address identifiers are added to the data (using encapsulation) as it travels down the protocol stack on the source host.

Getting the Data to the End DeviceFocusing on Layer 2 PDU – Frame…

Host physical address, is contained in the header of the frame.

The physical address is also called the ______________________________

Layer 2 is concerned with the delivery of messages on a _____________ _______________________

The MAC address is unique on the local network and _______________________ _______________________________

Once a frame is successfully received by the destination host, the Layer 2 address information is removed as the data is decapsulated and moved up the protocol stack to Layer 3…

Layer 3 protocols are designed to ____ _____________________________________________ within an internetwork.

Layer 3 addresses must include _________ that enable intermediary network devices to _______________________________

Every _________________________ __________________________________________________________

___________ use the __________ identifier portion of this address to determine which path to use to reach the destination host.

Once the path is determined, the router encapsulates the packet in a new frame and sends it on its way toward the destination end device.

When the frame reaches its final destination, the frame and packet headers are removed and the data moved up to Layer 4.

Getting the Data Through the InternetworkFocusing on Layer 3 PDU – Packet…

Getting the Data To the Right Application At Layer 4, information contained in the PDU header

(segment) identifies the _____________________ _____________________________________________________________________________

Hosts can run ______________________________. Example: e-mail client running at the same time as a web browser,

an instant messaging program etc All these separately running programs are examples of individual

processes. Each application or service is _______________ at

Layer 4 by a ________________________ A unique dialogue between devices is identified with a pair of Layer 4 source and destination port numbers that are representative of the two communicating applications.

When the data is received at the host, the ____________ _____________________________________________________________________________________

Putting it all togetherOSI

Layer #

ISO LayerName

TCP/IP #

TCP/IP layer Name

Encapsulation Units

Devices or

Components

TCP/IP Protocols

Keywords/Description

7Application

(All)

4Application

data PC

FTP, HTTP, POP3, IMAP,

telnet, SMTP, DNS,

TFTP

Network services for application processes, such

as file, print, messaging, database services

6Presentation

(People) data    

Standard interface to data for the application layer.

MIME encoding, data encryption, conversion, formatting, compression

5Session(Seem)

data   

Interhost communication. Establishes, manages and

terminates connection between applications

4Transport

(To) 3Transport segments

TCP, UDP End-to-end connections and reliability.

Segmentation/desegmentation of data in proper

sequence. Flow control

3Network(Need) 2

Internet packetsrouter

IP Logical addressing and path determination.

Routing. Reporting delivery errors

2Data Link

(Data) 1Network Access

framesbridge, switch,

NIC  

Physical addressing and access to media. Two sublayers: Logical Link

Control (LLC) and Media Access Control (MAC)

1Physical

(Processing)bits

repeater, hub,

tranciever  

Binary transmission signals and encoding. Layout of

pins, voltages, cable specifications, modulation